This invention generally relates to inclinometers, especially to those used in backcountry skiing and snow science.
An inclinometer (aka clinometer, declinometer, slope meter, tilt meter, slope gauge, gradiometer, etc) is an instrument for measuring the angle of an object (or the angle between two points) with respect to gravity, or with respect to a horizontal plane. The inclination reading (or declination, slope angle, etc) is typically given in degrees from horizontal.
Inclinometers are used in a wide range of applications. In backcountry skiing and snow science in particular, inclinometers are commonly used to measure the angle of a snow-covered slope as an aid in assessing risk of avalanche. Avalanches tend to occur only within a certain range of slope angles, and estimating slope angle by eye (without an inclinometer) is difficult even for experienced backcountry skiers, so inclinometers are a valuable tool to those traveling in avalanche terrain.
Some forms of inclinometer work best by viewing the profile of a remote slope from the side in order to measure its angle (“sighting from the side” or “across” a slope), others work best when standing at the top or bottom of a slope and sighting up or down it to measure its angle (“sighting up or down”), and still others work best when used in direct contact with the slope being measured (“contact measurement”). Each of these use modes has unique benefits in different situations in backcountry skiing, but few models of existing inclinometer support all these use modes.
The types of inclinometer commonly used for backcountry skiing typically fall into the following categories:
(a) “Hand-held card” type (eg. BCA Slope Meter, per “BCA Slope Meter product page” in information disclosure): These work best for contact measurements and for sighting across a slope from the side. They are difficult to impossible to use for sighting up or down a slope.
(b) “Hand-held with mirror” type (eg. Suunto MC-2, per “Mirror Compases User Guide” in information disclosure): These are similar to the hand-held card type in function, but also include a mirror to facilitate sighting up or down a slope. These are typically sold as a compass with inclinometer feature. Though the mirror allows these to be used for sighting up or down a slope, the process of measuring slope angle in this way is somewhat tricky to master in practice.
(c) “Forestry” type (eg. Suunto PM-5, per “Precision Instruments User Guide” in information disclosure): These are highly accurate, but relatively bulky and heavy, and are very expensive. For measuring slope angle, they work best and most accurately when sighting up or down a slope.
(d) “Ski-pole-integrated” type (eg. K2 LockJaw series poles, per U.S. Pat. No. 8,677,639): These are similar in function to the hand-held card type, but are integrated into a ski pole. They have the advantage of being easily accessible when skiing (because ski poles are always in your hands). However, the only existing models (the K2 LockJaw series) can only feasibly be used for contact measurements. They are difficult to impossible to use for measuring slope angle by sighting up, down, or across a slope. The scale on these particular models also has a very limited measurement range, and is notoriously difficult to read.
(e) “Electronic” type (eg. Pieps 30° Plus, per “Pieps 30° Plus product page” in information disclosure): These are quite accurate but very expensive. They work best for contact measurements and for sighting from the side. They require batteries that have to be replaced when they run low. The Pieps 30° Plus model is designed to be attached to a ski pole for the advantage of easy access, but in practice it is somewhat bulky and cumbersome on the pole shaft.
More recently, a new type of ski pole inclinometer was proposed in the public domain, by two seemingly independent sources, as described below.
(f) “Straight-lined-sticker” type ski pole inclinometer (eg. Robana & Trampuz in information disclosure): I'll refer to these herein as “SLS” type inclinometers. An example of these is shown in FIG. 11. It comprises a sticker 1110 with straight lines 1112 printed on it and numbers 1114 identifying the angle of each line. When wrapped around a ski pole shaft 210 just below the pole's grip 212 as shown in FIG. 11B, this SLS type inclinometer is intended to allow measurement of slope angle when sighting across a slope. To do so the user holds the pole vertically with the profile of the slope to be measured 1116 in the background, and then looks for the line or lines 1112 on the sticker that appear to most closely match the profile of the slope being measured 1116. These SLS type ski pole inclinometers suffer from a significant oversight in geometry. When the sticker is wrapped around a pole shaft, a 2D projection (i.e. what's seen by the user, as illustrated in FIG. 11B) shows lines that are no longer straight, and do NOT accurately represent the same angles as the straight lines on the flat sticker. The end result is that these straight-lined-sticker type ski pole inclinometers are grossly inaccurate. In the example of FIG. 11B, the angle of the slope in the background 1116 is 32°, which clearly does not match the line marked “32” in the sticker image 1118. Using this particular SLS inclinometer, one might easily mis-measure the slope angle as 26° or so.
Another disadvantage of this type of inclinometer is that it is intended for measuring slope angles by sighting across the slope only, and cannot be used for sighting up or down a slope to measure its inclination.
Disclosed herein are embodiments of an apparatus that provide advantages over prior inclinometers.